Secondary node change measurement signaling in next generation radio network

ABSTRACT

The invention refers to a transfer of a User Equipment, UE, context within a secondary network from a secondary network node ( 110 A) to a new secondary network node ( 110 B), wherein the UE ( 105 ) is served by a master network node ( 120 ) and the secondary network node ( 110 A), the method comprising: the UE receiving a first message ( 1202 ) indicative measurement configuration constructed by the secondary network node ( 110 A); the UE performing, based on the measurement configuration, measurements of potential candidates for anew secondary network node ( 110 B); and the UE sending a second message ( 1203 ) comprising a measurement report indicative of the measurements of potential candidates for the new secondary node. The invention further relates to a secondary network node adapted to perform the method steps of initiating sending a first message ( 1202 ) indicative of a secondary network node measurement configuration to the UE ( 105 ); and receiving a second message ( 1203 ) comprising a measurement report indicative of the measurements of potential candidates for a new secondary node from the UE ( 105 ).

CROSS REFERENCE TO RELATED APPLICATION(S)

This application is a 35 U.S.C. § 371 National Phase Entry Applicationfrom PCT/EP2017/078185, filed Nov. 3, 2017, designating the UnitedStates, and also claims the benefit of U.S. Provisional Application No.62/417,724, filed Nov. 4, 2016, the disclosures of which areincorporated herein by reference in their entirety.

TECHNICAL FIELD

Disclosed herein are embodiments for handling a transfer of a UserEquipment, UE, context within a secondary network from a sourcesecondary network node to a target secondary network node; especially atransfer is considered for Long Term Evolution-New Radio interworking;further especially a measurement handling for such transfer isconsidered.

BACKGROUND

The Third Generation Partnership Project (3GPP) has started work on thedevelopment and design of the next generation mobile communicationssystem (a.k.a., the 5G mobile communication system or simply “5G” forshort). 5G will encompass an evolution of today's 4G networks and theaddition of a new, globally standardized radio access technology knownas “New Radio” (NR).

The large variety of requirements for NR implies that frequency bands atmany different carrier frequencies will be needed. For example, lowbands will be needed to achieve sufficient coverage and higher bands(e.g. Millimeter Wave, mmW, such as near and above 30 GHz) will beneeded to reach the required capacity. At high frequencies, thepropagation properties are more challenging and high order bcamformingat the base station (e.g., evolved NodeB, eNB, or NR NodeB, gNB) will berequired to reach sufficient link budget. For example, narrow beamtransmission and reception schemes may be needed at higher frequenciesto compensate the high propagation loss. For a given communication link,a beam can be applied at the transmission point (TRP) (i.e., a transmit(TX) beam) and a beam can be applied at the user equipment (UE) (i.e., areceive (RX) beam)), which collectively is referred to as a “beam pairlink” (BPL) or just “link” for short.

NR will have a beam centric design, which means that the traditionalcell concept is relaxed and user equipments (UEs) (fixed or mobilewireless communication devices) will in many cases be connected to andperform “handover” between narrow beams instead of cells. Hence, 3GPPhas agreed to study concepts for handling mobility between beams (bothwithin and between transmission points (TRPs)). In the following, suchmobility will also be referred to as beam based mobility; thepotentially high number of mobility beams will make handover much morecomplex that of LTE; e.g. it may be unfeasible for the UE to performpower measurement of all possible beams; instead of this there may be apreselection in the network of best suitable beams to be measured by theUE.

Overall requirements for the Next Generation (NG) architecture (see TR23.799, Study on Architecture for Next Generation, which is incorporatedherein by reference in its entirety) and, more specifically the NGAccess Technology (see TR 38.913, Study on Scenarios and Requirementsfor Next Generation Access Technologies, which is incorporated herein byreference in its entirety) may impact the design of 5G (see RP-160671,New SID Proposal: Study on New Radio Access Technology, DoCoMo, which isincorporated herein by reference in its entirety) from mobility tocontrol plane design and mechanisms.

SUMMARY

It is an object to design basic radio resource management (RRM)functions, such as mobility handling among Long Term Evolution (LTE)(e.g. Evolved Node B (eNB)), NR Radio nodes (e.g. gNB) entities, anduser equipments.

This object is achieved by the independent claims. Advantageousembodiments are described in the dependent claims and by the followingdescription.

Embodiments relate to the secondary node change and the reconfigurationof a new secondary node where the RRC protocol(s) of the sourcesecondary node and/or target secondary node are partially in charge ofthe secondary node change. Advantages of the proposed embodiments mayinclude minimization of the specification of NR related mobilitymeasurement configurations and procedures in LTE specifications and viceversa by distributing mobility management/control between MeNB and SgNBor MgNB and SeNB in case of LTE-NR interworking. An additional benefitis the LTE eNB does not need to implement NR related mobility proceduresand algorithms.

According to an embodiment, a method for a transfer of a User Equipment,UE, context within a secondary network from a source secondary networknode to a target secondary network node is provided, wherein the UE isserved by a master network node and the source secondary network node,the method comprising the following steps performed by the UE:

-   -   receiving a first message indicative of a secondary network node        measurement configuration;    -   based on the measurement configuration, performing measurements        of potential candidates for a target secondary network node; and    -   sending a second message comprising a measurement report        indicative of the measurements of potential candidates for a        target secondary node.

According to an embodiment, a User Equipment is provided, wherein the UEadapted to perform above-described method.

According to an embodiment, a User Equipment, UE is provided that isconfigured for supporting a transfer of a UE context within a secondarynetwork from a source secondary network node to a target secondarynetwork node, wherein the UE is served by a master network node and thesource secondary network node, the UE comprising a transmitter; areceiver; a memory; and a data processing system comprising one or moreprocessors, wherein the UE is configured to perform the steps of:

-   -   receiving a first message indicative of a secondary network node        measurement configuration;    -   based on the measurement configuration, performing measurements        of potential candidates for a target secondary network node; and    -   sending a second message comprising a measurement report        indicative of the measurements of potential candidates for a        target secondary node.

According to an embodiment, a method for a transfer of a User Equipment,UE, context within a secondary network from a source secondary networknode to a target secondary network node is provided, wherein the UE isserved by a master network node and the source secondary network node,the method comprising the following steps performed by the sourcesecondary network node:

-   -   initiating sending a first message indicative of a secondary        network node measurement configuration to the UE; and    -   receiving a second message comprising a measurement report        indicative of the measurements of potential candidates for a        target secondary node from the UE.

According to an embodiment, a network node is provided that is adaptedto perform the above-described method.

According to an embodiment, a network node is provided that isconfigured for providing a transfer of a UE context within a secondarynetwork to a target secondary network node, wherein the UE is served bya master network node and the network node, the network node comprisinga transmitter; a receiver; a memory; and a data processing systemcomprising one or more processors, wherein the network node isconfigured to perform the steps of.

initiating sending a first message indicative of a secondary networknode measurement configuration to the UE; and

receiving a second message comprising a measurement report indicative ofthe measurements of potential candidates for a target secondary nodefrom the UE.

BRIEF DESCRIPTION OF THE DRAWINGS

Further details of embodiments are described with reference to thedrawings, wherein:

FIG. 1 illustrates an exemplary wireless communications system accordingto some embodiments.

FIG. 2 illustrates a prior art signaling diagram.

FIG. 3 illustrates a prior art signaling diagram.

FIG. 4 illustrates a prior art signaling diagram.

FIG. 5 illustrates a prior art signaling diagram.

FIG. 6 illustrates a signaling diagram according to some embodiments.

FIG. 7 illustrates a signaling diagram according to some embodiments.

FIG. 8 illustrates an exemplary flow chart according to someembodiments.

FIG. 9 illustrates an exemplary flow chart according to someembodiments.

FIG. 10 is a block diagram of a secondary network node according to someembodiments.

FIG. 11 is a block diagram of a master network node according to someembodiments.

FIG. 12 illustrates a signaling diagram according to some embodiments.

DETAILED DESCRIPTION

FIG. 1 illustrates an exemplary wireless communications system accordingto some embodiments. Wireless communications system 100 may comprise aUser Equipment 105 (i.e., fixed or mobile wireless communication device)and one or more base stations, including a master radio resource control(RRC) network node 120, and a plurality of secondary RRC network nodes110A-B. In some embodiments, the master network node 120 and thesecondary network nodes 110A-B are further in communication with a corenetwork 130. In some embodiments, the master network node 120 maycomprise a master Evolved Node B as known in LTE networks (referred toherein as MeNB), and the secondary network nodes 110A-B may comprisesecondary New Radio (NR) RRC entities for the next generation/5G accesstechnologies (referred to herein as SgNB). In other embodiments, themaster network node 120 may comprise a master NR network node (referredto herein as MgNB) and the secondary network nodes 110A-B may comprisesecondary eNBs (referred to herein as SeNB).

In some embodiments, the master network node 120 may serve the UE 105 asindicated by link 115A. In some embodiments, a secondary network node110A-B may further provide additional resources for the UE 105, such asserving cells. For example, a secondary network node 110A-B may provideadditional resources based on a received measurement report, trafficconditions, or bearer types. Thus, in some embodiments, UE 105 may beserved by both a master network node 120 and a source secondary networknode 110A, as illustrated by links 115A and 115B. However, in someembodiments, it may be desirable to switch from the source secondarynetwork node 110A to a target secondary network node 110B, in which casethe UE may be served by both the master network node 120 and the targetsecondary network node 110B after a secondary network node transfer, asillustrated by links 115A and 115C.

LTE Dual Connectivity

In LTE Dual Connectivity (DC), thanks to the mutual intelligibilitybetween master and secondary network nodes (MeNB 120 and SeNB 110A), theMeNB 120 is able to maintain the RRM measurement configuration of the UE105 for mobility procedures. Furthermore, the MeNB 120 may decide to aska SeNB 110A to provide additional resources (serving cells) for a UE 105e.g., based on the received measurement reports or traffic conditions orbearer types as it is straightforward the interpret those by the RRCentity located at the master network node 120. Therefore, the mobilitycan mainly be coordinated by the MeNB 120 in case of LTE DC.

FIGS. 2-5 are prior art signaling diagrams for LTE DC based on 3GPP TS36.300, which is incorporated by reference herein in its entirety. Asillustrated in FIG. 2 , the SeNB Addition procedure for LTE DC isinitiated by the MeNB 120 and is used to establish a UE context at theSeNB 110A in order to provide radio resources from the SeNB 110A to theUE 105. This procedure is used to add at least the first cell, i.e.,PSCell of the Secondary Cell Group (SCG) in case of LTE DC. As shown inFIG. 2 , the MeNB 120 may transmit a first message 201, which is a SeNBRequest (carry SCG-ConfigInfo) message. The SCG-ConfigInfo may includethe MeNB 120 configuration and the entire UE 105 capabilities for UEcapability coordination to be used as a basis for the reconfiguration bythe SeNB. Next, the SeNB 110A may transmit a second message 203, whichis a SeNB Addition Request Acknowledge (Carry SCG-Config) message. TheSCG-Config may include the new radio resource of SCG, including radioconfiguration information and data forwarding address information (ifapplicable). Next, to perform the handover, the MeNB 120 may transmit athird message 205 to the UE 105, which is a RRCConnectionReconfigurationmessage. Next, the UE 105 may transmit a fourth message 207 back to theMeNB 120, the fourth message comprising aRRCConnectionReconfigurationComplete message. Finally, the MeNB 120 maytransmit a fifth message 209 to the SeNB 110A comprising aReconfiguration Complete message.

FIGS. 3-4 illustrate a SeNB 110A release procedure for LTE DC. The SeNBRelease procedure may be initiated either by the MeNB 120 or the SeNB110A and is used to initiate the release of the UE context at the SeNB.The recipient node of this request cannot reject. The SeNB Releaseprocedure does not necessarily need to involve signaling towards the UE,e.g., RRC reconnection re-establishment due to Radio Link Failure inMeNB 120. FIG. 3 illustrates a release procedure initiated by the MeNB120, and FIG. 4 illustrates a release procedure initiated by the SeNB110A. As shown in FIG. 3 , the MeNB 120 initiates the release procedureof the SeNB 110A by transmitting a first message 301 to the SeNB 110A,the first message being a SeNB Release Request. The SeNB Release Requestmay trigger the source SeNB 110A to stop providing user data to the UE105, and if applicable, to start data forwarding. The MeNB 120 thentransmits message 303 to the UE 105 comprising a RRCConnectionReconfiguration, and the UE responds and transmits message 305to the MeNB 120 confirming RRCConnectionReconfiguration Complete. Asshown in FIG. 4 , the SeNB 110A initiates the release procedure bytransmitting a first message 401 to the MeNB 120 comprising a SeNBRelease Required. The MeNB 120 then transmits message 403 to the SeNB110A comprising a SeNB Release Confirm. The MeNB 120 then transmitsmessage 405 to the UE 105 comprising a RRC ConnectionReconfiguration,and the UE responds and transmits message 407 to the MeNB 120 confirmingRRCConnectionReconfiguration Complete.

FIG. 5 illustrates how a SeNB change procedure may be initiated by aMeNB 120 and used to transfer a UE context from a source SeNB 110A to atarget SeNB 110B, as well as change the SCG configuration in the UE fromthe source SeNB 110A to the target SeNB 110B. As shown in FIG. 5 , theLTE SeNB change procedure may be initiated by a MeNB 120 transmittingmessage 501, a SeNB Addition Request, towards a target SeNB 110B via thesource SeNB 110A. In response, the target SeNB 110B may transmit message503, a SeNB Addition Request Acknowledgement towards the MeNB 120 viathe source SeNB 110A. The MeNB 120 may transmit message 505, a SeNBRelease Request, to the source SeNB 110A, which the recipient SeNB 110Acannot reject. The MeNB 120 may then transmit message 507, aRRCConnectionReconfiguration message towards the UE 105, and in responsereceive message 509, a RRCConnectionReconfigurationComplete message fromthe UE 105. The MeNB 120 may further send message 511, a SeNBReconfiguration Complete message towards the target SeNB 110B.

Secondary Node Configuration in Case of LTE-NR Interworking

In case of secondary node modification, or node change, or releaseprocedures, the master node may not necessarily maintain the radioresource management, RRM, measurement configuration of the UE for thesecondary node, but may only generate a final RRC message. The RRCmessage transmitted from the master node may contain the RRC PDU whichis of an RRM measurement configuration prepared by the RRC entity in thesecondary node. Whether the master node needs to understand the RRMmeasurement configuration or not may be left to the implementation.

In case of secondary node modification, node change, or releaseprocedures, the RRM measurement report related to the mobility withinthe secondary node(s) may be received by the master node (RRC entity ofthe master node) a final RRC message. In a first option, the masternode, without needing to parse the information, may transfer the NR partof the RRC message including the RRM measurement report, e.g., over X2*interface, to the secondary node (e.g. to the RRC entity located in thesecondary node), e.g. by means of a container. In a second option, if adirect SRB is allowed between the secondary node and UE, the measurementreport may be sent directly between the UE and the secondary node.

FIGS. 5 and 6 show two options, e.g. called option A and option B, forthe secondary node change and the reconfiguration of a new secondarynode, wherein the RRC protocol of a secondary node is partially incharge of the secondary node change.

In both Options, different from LTE DC, secondary node change (SgNB) maybe initiated by the secondary node (e.g. S-SgNB) instead of the masternode (MeNB). As NR mobility is expected to be different from mobility inLTE, the mobility algorithms may cope with the beam based mobility.

In Option A, not all the secondary node (SgNB) change signaling has togo through the master node (MeNB), whereas in Option B, all thesignaling relevant to secondary node (SgNB) change goes via the masternode (MeNB), allowing it to understand all the signaling steps; it maydepend on the implementation, how deep the master node shall understandthe signalling. In either case, if the procedure is not intercepted bymaster node (MeNB), the target secondary node (e.g. T-SgNB),configuration info e.g., NR-Configuration Information (or brieflyNR-Config Info), is sent to the UE via a final RRC message from MeNB.

Thus, target secondary node configuration info (T-SgNB NR-Config Info)may be (completely or partially) transparent to the MeNB that sends suchconfiguration information to the UE in a final LTE RRC message.

LTE-NR Secondary Network Node Change

RRC diversity may be envisioned for both the downlink and uplink toaddress aforementioned challenges e.g. related to Ultra-Reliable and LowLatency Communications (URLLC) and mobility robustness.

NR RRM is expected to be different than LTE RRM due to above-discussedbeam based mobility. Especially NR RRM measurement configuration,measurement reporting events and triggers may be rather different thanthose already specified for LTE mobility. It may e.g. be preferablekeeping the LTE and NR RRMs self-contained, e.g. to enable afuture-proof NR RRM design e.g., when NR stand-alone operation isconsidered.

In the following, it is described an exemplary set of embodimentsrelated to the secondary network node change and the reconfiguration ofa new secondary network node where the RRC protocol(s) of the sourcesecondary network node and/or target secondary network node arepartially in charge of the secondary network node change. Minimizationof the specification of NR related mobility measurement configuration inLTE specifications and vice versa may be achieved by distributingmobility management/control between MeNB 120 and SgNB 110A-B (or MgNB120 and SeNB 110A-B) in case of LTE-NR interworking

The disclosure proposes two major options for the secondary network nodechange and the reconfiguration of a new secondary network node where theRRC protocol(s) of the source secondary network node and/or targetsecondary network node are partially in charge of the secondary networknode change as shown in FIGS. 6-7 . These options are different from LTEDC, as described above, because, for example, the SgNB Change isinitiated by the S-SgNB 110A instead of the MeNB 120. Additionally, inboth options, the target SgNB configuration may be transparent to theMeNB. It may be desirable for the SgNB change to be initiated by theS-SgNB 110A since NR mobility is expected to be different than LTE andthe mobility algorithms may be beam based mobility. It may be expectedthat the entity deciding NR mobility may reside in the NR part of the 5GRAN, i.e., within a gNB, which may include knowledge about NR radioresource topology in the neighborhood, current NR radio resource status,and controlling and processing NR related UE measurements. Theprocedures described below proposes a solution where the LTE and NRrelated logical nodes of the 5G RAN are distinct, separate logicalentities, inter-connected via an interface that is called “X2*.”

First, the master network node 120, such as the MeNB 120 in FIG. 6 ,determines one or more suitable candidates to be the SgNB. This may bebased on downlink (DL) measurements or uplink (UL) measurements.

In the case of a DL measurement based procedure, the SgNB determines thesuitable measurement configuration for the UE including suitableinter-frequencies to measure. In addition, need of measurement gaps canbe determined based on the UE capability. The SgNB constructs themeasurement (RRC) configuration. The configuration is sent to the UEeither directly or via MeNB. The first solution is only possible if thedirect SRBs between SgNB and UE are supported. In the latter solution,MeNB sends the final RRC message to the UE. After the UE has measuredpotential candidates for new SgNB, the UE sends a measurement report tothe network. This may be sent to the SgNB directly in case SRB betweenUE and SgNB is supported. If the measurement report is sent to the MeNB,the MeNB forwards the measurement results to the SgNB via X2 or X2*.

In the case of UL measurement based procedure, the decision to changeSgNB may be performed in the original SgNB. The UE may be potentiallyconfigured with UL signal to be used for mobility. The signal may besimilar to SRS. Depending on the solution, the UL signal configurationcan be sent via RRC to the MeNB or SgNB directly. The SgNB can directlyreceive UL signal from the UE, and based on that determine suitablecandidate(s) for the SgNB change. In cases where the MeNB receives theUL signal, the MeNB may forward the measurement result to the SgNB.

FIG. 12 shows an exemplary signaling diagram with respect toabove-described measurement configuration. The master network node 120receives a measurement configuration information 1201 constructed by thecurrent (or source) secondary network node, e.g. S-SgNB 110A. The masternetwork node 120 constructs a final RRC message 1202 comprising thereceived measurement configuration and sends it to the UE 105. Based onthe measurement configuration, UE 105 performs measurements of potentialcandidates for a new secondary network node e.g. T-SgNB 110B. Finally,the UE responds with a measurement report message 1203 comprising themeasurement report indicative of the measurements of potentialcandidates for the new secondary node. The master network node sends ameasurement report 1204 comprising the measurement results to thecurrent (or source) secondary network node 110A that determines, basedon the measurement report, the new (or target) secondary network node110B.

Once the target SgNB is determined, the signaling to change the SgNBtakes place as described below in connection with FIG. 6 or FIG. 7 .

As shown in FIG. 6 , the SgNB change is initiated by the S-SgNB 110Asending message 601, a SgNB Handover Request message, to T-SgNB 110Bwithout passing it through the MeNB 120. NR-Config information includedwithin the Handover Request 601 message may be used by the S-SgNB 110Ato request the T-SeNB 110B to perform certain configuration actions,similar to those performed via LTE SCG-ConfigInfo and/or HandoverRequest in LTE. Next, the T-SgNB 110B replies back to the S-SgNB 110Awith message 603, a SgNB Handover Response message including the NRconfiguration e.g., NR-Config. NR-Config may include the new radioresource associated with the T-SgNB 110B. The S-SgNB 110A then sendsmessage 605 with the NR-Config information to MeNB 120. Message 605 maybe an X2* AP message, called SgNB Change Request in FIG. 6 , in order toenable the RRC reconfiguration of the UE 105 with the T-SgNB 110B. Thesame X2*AP message 605 may include information on the user plane switchso as to be able to successfully execute the SgNB change and activateuser plane data flow toward UE 105. The NR configuration message (e.g.,NR-Config), may be used to transfer the radio configuration generated bythe T-SgNB 110B. Upon receiving the NR configuration via message 605,the MeNB 120 may (i) intercept, and send message 607, a SgNB changereject to the S-SgNB 110A, which in turn sends message 609, SgNB ChangeReject to the T-SgNB 110B, or (ii) proceed by transmitting message 611,a SgNB Release Request, to the S-SgNB 110A. In the second case, the MeNB120 may perform RRC Connection Reconfiguration steps, includingtransmitting message 613, a RRCConnectionReconfiguration message, to theUE 105, the UE 105 transmitting message 615, aRRCConnectionReconfigurationComplete message, to the MeNB 120, and theMeNB 120 transmitting message 617, a SgNB Reconfiguration Completemessage, to the T-SgNB 110B to complete the SgNB transfer procedure.

FIG. 7 illustrates a second signaling diagram according to someembodiments. As shown in FIG. 7 , the SgNB change procedure is initiatedby the S-SgNB 110A, but the signaling goes via the MeNB 120. The S-SgNB110A initiates the SgNB change procedure by transmitting message 701, aSgNB Change Request with NR Config Info message, to the MeNB 120. TheMeNB 120 may then reject the SeNB change by transmitting message 703, aSgNB Change Reject message, or proceed with the change by transmittingmessage 705, a SgNB Addition Request (include NR-Config Info) message,towards the T-SgNB 110B. In the latter case, the T-SgNB 110B may respondto message 705 by transmitting towards the MeNB 120 message 707, a SgNBAddition Request Acknowledgement message, which includes the NR-ConfigInfo for the T-SgNB 110B. In response to message 707, the MeNB 120 maytransmit message 711, a SgNB Change Request Acknowledgement (includeNR-Config Info) to the S-SgNB 110A, as well as transmit message 713, aSgNB Release Request message, to the S-SgNB 110A. The MeNB 120 mayperform RRC Connection Reconfiguration steps, including transmittingmessage 715, a RRCConnectionReconfiguration message, to the UE 105, theUE 105 transmitting message 717, a RRCConnectionReconfigurationCompletemessage, to the MeNB 120, and the MeNB 120 transmitting message 719, aSgNB Reconfiguration Complete message, to the T-SgNB 110B to completethe SgNB transfer procedure.

Depending on the implementation and which messages the MeNB 120 canpartially or fully understand e.g., SgNB Change Request or SgNB AdditionRequest Acknowledge, the MeNB 120 may intercept the procedure e.g.,proceed with/reject the SeNB change earlier as shown in FIG. 7 ascompared to the other option as shown in FIG. 6 . However, in someembodiments, the procedure shown in FIG. 6 may be more desirable whereforcing each signal to go through MeNB 120 may increase signalingoverhead and latency for the SgNB change procedure. On the other hand,it may also be advantageous to allow a central entity to overlook theoverall mobility behavior and respective RRM strategy due to, forexample, the fact that mobility of the RRC connection that is controlledby the MeNB needs to be taken into account. Apart from that, the secondoption shown in FIG. 7 would be able to reuse existing LTE framework.

In some embodiments, the NR configuration message, e.g., NR-Config Infoin messages 603, 706, may be an RRC Protocol Data Unit (PDU) transferredbetween UE RRC entity and NR RRC entity. Yet in another embodiment, suchinformation could be comprised by an information element (IE) similar toSCG-Config in LTE DC.

In another option/embodiment, the LTE-NR interworking scenario as shownin FIGS. 6-7 could be other way around such, that a NR node is themaster network node 120 (i.e., MgNB 120), and LTE nodes are the sourceand target secondary network nodes (i.e., S-SeNB 110A and T-SeNB 110Band/or S-SgNB and T-SgNB). In some embodiments, the configuration may betransferred directly from the S-SgNB to the UE instead of transferringit via the MeNB. In another embodiment, the involved 5G RAN nodes couldbe nodes that support both LTE and NR access, hence, each entity couldbe in the position to comprehend and process RRC messages and performrespective RRM actions. Yet, in another embodiment, the scenario couldbe the same as shown in FIGS. 6-7 , and MeNB 120 can in parallel add anSgNB or change an SgNB by following the existing LTE DC procedures, ascan be found in 3GPP TS 36.300.

FIG. 8 is an exemplary flow diagram according to some embodiments. Inpreferred embodiments, method 800 is performed by the source secondarynetwork node 110A as described in connection with FIG. 10 to transfer aUE context from the source secondary network node 110A to a targetsecondary network node 110B that is different than the source secondarynetwork node 110B.

In step 801, the source secondary network node 110A transmits a firstmessage to the target secondary network node 110B, wherein the targetnetwork node 110B is configured to respond to the first message bytransmitting to the source secondary network node 110A a second messagecomprising configuration data of the target secondary network node 110B.

In step 803, the source secondary network node 110A receives the secondmessage transmitted by the target secondary network node 110B.

In step 805, after receiving the second message, the source secondarynetwork node 110A initiates a transfer of the UE context from the sourcesecondary network node 110A to the target secondary network node 110B,wherein initiating the transfer of the UE context comprises the sourcesecondary network node 110A transmitting to a master network node 120 athird message comprising the configuration data of the target secondarynetwork node.

In some embodiments, the first message in step 801 may comprise aHandover Request message 601 as shown in FIG. 6 , the Handover Requestmessage instructing the target secondary network node 110B to performone or more configuration actions. In some embodiments, the secondmessage in steps 801 and 803 of method 800 may comprise a HandoverResponse message, such as the Handover Request Ack message 603 as shownin FIG. 6 . In some embodiments, the configuration data in the secondmessage may comprise NR-Config Info, which may be one of a RRC PDU or anIE. In some embodiments, the source secondary network node 110B mayreceive a fourth message transmitted by the master network node 120 inresponse to the master network node 120 receiving the third message. Thefourth message may be a Release Request, such as message 611 shown inFIG. 6 .

FIG. 9 is an exemplary flow diagram according to some embodiments. Inpreferred embodiments, method 900 is performed by the master networknode 120 as described below in connection with FIG. 11 .

In step 901, the master network node 120 receives a first messagetransmitted by the source secondary network node 110A, the first messagecomprising a request to initiate a transfer of the UE context from thesource secondary network node 110A to the target secondary network node110B. In some embodiments, the first message may comprise a ChangeRequest, such as message 701 as shown in FIG. 7 .

In step 903, in response to the request, the master network node 120transmits a second message to the target secondary network node 110B.

In step 905, the master network node 120 receives a third message fromthe target secondary network node 110B, the third message comprisingconfiguration data of the target secondary network node 110B. In someembodiments, the configuration data of the target secondary network node110B may comprise NR-Config Info, which may comprise one of a RRC PDU oran IE.

In some embodiments, method 900 may further comprise the master networknode 120 transmitting an acknowledgement of the request to the secondarynetwork node 110A, such as message 711 shown in FIG. 7 . In someembodiments, method 900 may further comprise the master network node 120transmitting a release request to the source secondary network node110A, such as message 713 shown in FIG. 7 . In some embodiments, method900 may further comprise the master network node 120 transmitting amessage to the UE 105 in response to receiving the third message, themessage comprising an RRC Connection Reconfiguration,(RRCConnectionReconfiguration) message such as message 715 shown in FIG.7 . The method 900 may further comprise the master network node 120receiving a message from the UE 105, the message comprising an RRCConnection Reconfiguration Complete (RRCConnectionReconfigurationComplete) message such as message 717 shown in FIG. 7 . In someembodiments, the method 900 may further comprise the master network node120 transmitting to the target secondary network node 110B aReconfiguration Complete message, such as message 719 shown in FIG. 7 .

In connection with FIGS. 8-9 , in some embodiments, the source secondarynetwork node 110A comprises a first New Radio Node, the target secondarynetwork node 110B comprises a second New Radio Node, and the masternetwork 120 node comprises an eNB. In other embodiments, the sourcesecondary network node 110A comprises a first eNB, the target secondarynetwork node 110B comprises a second eNB, and the master network node120 comprises a New Radio Node.

FIG. 10 is a block diagram of a source secondary network node 110Aaccording to some embodiments. As shown in FIG. 10 , source secondarynetwork node 110A may comprise: a data processing system (DPS) 1002,which may include one or more processors 1055 (e.g., a general purposemicroprocessor and/or one or more other data processing circuits, suchas an application specific integrated circuit (ASIC), field-programmablegate arrays (FPGAs), and the like); a network interface 1005 for use inconnecting source secondary network node 110A to network 130; a radiotransceiver 1007 (i.e., a receiver and a transmitter) coupled to anantenna 1022 for use in, for example, wirelessly communicating with UEsand other devices; and local storage unit (a.k.a., “data storagesystem”) 1012, which may include one or more non-volatile storagedevices and/or one or more volatile storage devices (e.g., random accessmemory (RAM)). In embodiments where source secondary network node 110Aincludes a general-purpose microprocessor, a computer program product(CPP) 1041 may be provided. CPP 1041 includes a computer readable medium(CRM) 1042 storing a computer program (CP) 1043 comprising computerreadable instructions (CRI) 1044. CRM 1042 may be a non-transitorycomputer readable medium, such as, but not limited, to magnetic media(e.g., a hard disk), optical media (e.g., a DVD), memory devices (e.g.,random access memory), and the like. In some embodiments, the CRI 1044of computer program 1043 is configured such that when executed by dataprocessing system 1002, the CRI causes the source secondary network node110A to perform steps described above (e.g., steps described above withreference to the flow charts). In other embodiments, secondary networknode 110A may be configured to perform steps described herein withoutthe need for code. That is, for example, data processing system 1002 mayconsist merely of one or more ASICs. Hence, the features of theembodiments described herein may be implemented in hardware and/orsoftware.

FIG. 11 is a block diagram of a master network node 120 according tosome embodiments. As shown in FIG. 11 , master network node 120 maycomprise: a data processing system (DPS) 1102, which may include one ormore processors 1155 (e.g., a general purpose microprocessor and/or oneor more other data processing circuits, such as an application specificintegrated circuit (ASIC), field-programmable gate arrays (FPGAs), andthe like); a network interface 1105 for use in connecting master networknode 120 to network 130; a radio transceiver 1107 coupled to an antenna1122 for use in, for example, wirelessly communicating with UEs andother devices; and local storage unit (a.k.a., “data storage system”)1112, which may include one or more non-volatile storage devices and/orone or more volatile storage devices (e.g., random access memory (RAM)).In embodiments where master network node 120 includes a general purposemicroprocessor, a computer program product (CPP) 1141 may be provided.CPP 1141 includes a computer readable medium (CRM) 1142 storing acomputer program (CP) 1143 comprising computer readable instructions(CRI) 1144. CRM 1142 may be a non-transitory computer readable medium,such as, but not limited, to magnetic media (e.g., a hard disk), opticalmedia (e.g., a DVD), memory devices (e.g., random access memory), andthe like. In some embodiments, the CRI 1144 of computer program 1143 isconfigured such that when executed by data processing system 1102, theCRI causes the master network node 120 to perform steps described above(e.g., steps described above with reference to the flow charts). Inother embodiments, master network node 120 may be configured to performsteps described herein without the need for code. That is, for example,data processing system 1102 may consist merely of one or more ASICs.Hence, the features of the embodiments described herein may beimplemented in hardware and/or software.

In the following various embodiments will be exemplarily described.

Secondary Network Node Embodiments:

E1. A method performed by a source secondary network node to transfer aUser Equipment context from the source secondary network node to atarget secondary network node that is different than the sourcesecondary network node, the method comprising:

transmitting, by the source secondary network node, a first message tothe target secondary network node, wherein the target network node isconfigured to respond to the first message by transmitting to the sourcesecondary network node a second message comprising configuration data ofthe target secondary network node;

receiving, at the source secondary network node, the second messagetransmitted by the target secondary network node; and after receivingthe second message, initiating a transfer of the UE context from thesource secondary network node to the target secondary network node,wherein initiating the transfer of the UE context comprisestransmitting, by the source secondary network node, to a master networknode a third message comprising the configuration data of the targetsecondary network node.

E2. The method of embodiment 1, wherein the first message comprises aHandover Request message, the Handover Request message instructing thetarget secondary network node to perform one or more configurationactions.

E3. The method of embodiment 2, wherein the second message comprises aHandover Response message.

E4. The method of anyone of embodiments 1-2, wherein the configurationdata comprises one of: a radio resource control (RRC) protocol data unit(PDU) or an information element (IE).

E5. The method of anyone of embodiments 1-4, further comprising:

receiving, at the source secondary network node, a fourth messagetransmitted by the master network node, the fourth message comprising aRelease Request, wherein the master network node is configured totransmit the fourth message after receiving the third message.

E6. The method of anyone of embodiments 1-5, wherein the sourcesecondary network node comprises a first New Radio Node, the targetsecondary network node comprises a second New Radio Node, and the masternetwork node comprises an Evolved Node B.

E7. The method of anyone of embodiments 1-5, wherein the sourcesecondary network node comprises a first Evolved Node B, the targetsecondary network node comprises a second Evolved Node B, and the masternetwork node comprises a New Radio Node.

E8. A source secondary network node, comprising a transmitter; areceiver; a memory; and

a data processing system comprising one or more processors, wherein thesource secondary network node is configured to perform the method ofanyone of embodiments 1-7.

Master Network Node Embodiments

E1. A method performed by a master network node to transfer a UserEquipment context from a source secondary network node to a targetsecondary network node that is different than the source secondarynetwork node, the method comprising:

receiving, at the master network node, a first message transmitted bythe source secondary network node, the first message comprising arequest to initiate a transfer of the UE context from the sourcesecondary network node to the target secondary network node;

in response to the request, transmitting, by the master network node, asecond message to the target secondary network node; and

receiving, by the master network node, a third message from the targetsecondary network node, the third message comprising configuration dataof the target secondary network node.

E2. The method of embodiment 1, further comprising:

transmitting, by the master network node, a fourth message to the sourcesecondary network node, the fourth message comprising an acknowledgementof the request.

E3. The method of embodiment 2, further comprising:

transmitting, by the master network node, a fifth message to the sourcesecondary network node, the fifth message comprising a Release Request.

E4. The method of anyone of embodiments 1-3, further comprising:

in response to receiving the third message, transmitting a fourthmessage to the User Equipment, the fourth message comprising aRRCConnectionReconfiguration message; and

receiving a fifth message from the User Equipment, the fifth messagecomprising a RRCConnectionReconfiguration Complete message.

E5. The method of embodiment 4, further comprising:

in response to receiving the fifth message, transmitting, to the targetsecondary network node, a sixth message, the sixth message comprising aReconfiguration Complete.

E6. The method of anyone of embodiments 1-5, wherein the first messagecomprises a Change Request.

E7. The method of anyone of embodiments 1-6, wherein the configurationdata of the target secondary network node comprises one of: a radioresource control (RRC) protocol data unit (PDU) or an informationelement.

E8. The method of anyone of embodiments 1-7, wherein the sourcesecondary network node comprises a first New Radio Node, the targetsecondary network node comprises a second New Radio Node, and the masternetwork node comprises an Evolved Node B.

E9. The method of anyone of embodiments 1-7, wherein the sourcesecondary network node comprises a first Evolved Node B, the targetsecondary network node comprises a second Evolved Node B, and the masternetwork node comprises a New Radio Node.

E10. A master network node, comprising: a transmitter; a receiver; amemory; and a data processing system comprising one or more processors,wherein the master network node is configured to perform the method ofanyone of embodiments 1-9.

While various embodiments of the present disclosure are describedherein, it should be understood that they have been presented by way ofexample only. Additionally, while the processes described above andillustrated in the drawings are shown as a sequence of steps, this wasdone solely for the sake of illustration. Accordingly, it iscontemplated that some steps may be added, some steps may be omitted,the order of some steps may be re-arranged, and some steps may beperformed in parallel.

The invention claimed is:
 1. A method for transfer of a User Equipment,UE, context within a secondary network from a source secondary networknode to a target secondary network node, wherein the UE is served by amaster network node and the source secondary network node, the methodcomprising: the UE receiving a first message comprising a measurementconfiguration constructed by the source secondary network node; the UEperforming, based on the received measurement configuration,measurements of potential candidates for a target secondary networknode; and the UE sending a second message comprising a measurementreport indicative of the measurements of potential candidates for thetarget secondary network node.
 2. The method of claim 1, wherein thefirst message is received from the master network node, the firstmessage comprising the received measurement configuration.
 3. The methodof claim 1, wherein the received measurement configuration is indicativeof suitable inter-frequencies to measure, and wherein the UE performs acorresponding measurement.
 4. The method of claim 1, wherein the firstmessage is generated by an RRC entity within the source secondarynetwork node.
 5. The method of claim 1, wherein the UE receives themeasurement configuration in form of a RRC packet data unit, PDU.
 6. Themethod of claim 1, wherein the second message is sent to the masternetwork node.
 7. The method of claim 1, wherein the UE generates thesecond message comprising the measurement report in a container to beforwarded to the source secondary network node.
 8. The method of claim1, wherein in response to a decision of the source secondary network oftransferring the context from the source secondary network node to thetarget secondary network node, the UE receives a third messagecomprising a connection reconfiguration message.
 9. The method of claim8, wherein the third message is received from the master network node.10. The method of claim 8, wherein the third message comprises asecondary node configuration generated by the target secondary networknode.
 11. The method of claim 1, wherein the UE transmits a fourthmessage comprising a connection reconfiguration complete confirmation inresponse to the third message.
 12. The method of claim 11, wherein thefourth message is transmitted to the master network node.
 13. The methodof claim 11, wherein transmitting the fourth message initiates sending afifth message comprising a connection reconfiguration completeinformation from the master network node to the target secondary networknode.
 14. The method of claim 1, wherein the measurement configurationis maintained by the source secondary network node.
 15. A UserEquipment, UE configured for supporting a transfer of a UE contextwithin a secondary network from a source secondary network node to atarget secondary network node, wherein the UE is served by a masternetwork node and the source secondary network node, the UE comprising: atransmitter; a receiver; a memory; and a data processing systemcomprising one or more processors, said memory comprising instructionsexecutable by said one or more processors, wherein the UE is operativeto: receive a first message comprising a measurement configurationconstructed by the source secondary network node; perform based on thereceived measurement configuration, measurements of potential candidatesfor the target secondary network node; and send a second messagecomprising a measurement report indicative of the measurements ofpotential candidates for the target secondary network node.
 16. The UEof claim 15, wherein the UE is configured to perform a measurement ofsuitable inter-frequencies.
 17. The UE of claim 15, wherein the secondmessage is sent to the master network node.
 18. The UE of claim 15,further being operative to generate the second message comprising themeasurement report in a container to be forwarded to the sourcesecondary network node.
 19. The UE of claim 15, further being operativeto: receive a third message comprising a connection reconfiguration, andtransmit a fourth message comprising a Connection ReconfigurationComplete confirmation.
 20. The UE of claim 19, wherein the third messageis received from the master network node.
 21. A method for transfer of aUser Equipment, UE, context within a secondary network from a sourcesecondary network node to a target secondary network node, wherein theUE is served by a master network node and the source secondary networknode, the method comprising the following steps performed by the sourcesecondary network node: initiating sending a first message comprising asecondary network node measurement configuration to the UE; andreceiving a second message comprising a measurement report indicative ofthe measurements of potential candidates for a target secondary networknode from the UE.
 22. The method of claim 21, wherein the first messageis transmitted to the master network node to be forwarded to the UE. 23.The method of claim 21, wherein the measurement configuration isindicative of suitable inter-frequencies to be measured by the UE. 24.The method of claim 21, wherein the second message is received from themaster network node, the second message comprising the measurementreport of the UE.
 25. The method of claim 21, further comprisingretrieving the measurement report from a container comprised by thesecond message.
 26. The method of claim 21, further comprising thefollowing step performed by the source secondary network node:constructing the secondary network node measurement configuration.
 27. Asource secondary network node, configured for providing a transfer of aUE context within a secondary network to a target secondary networknode, wherein the UE is served by a master network node and the sourcesecondary network node, the source network node comprising: atransmitter; a receiver; a memory; and a data processing systemcomprising one or more processors, said memory comprising instructionsexecutable by said one or more processors, wherein the source secondarynetwork node is operative to: initiate sending a first messagecomprising a secondary network node measurement configuration to the UE;and receive a second message comprising a measurement report indicativeof the measurements of potential candidates for a target secondarynetwork node from the UE.